This invention relates to a method for the preparation of oxy-diphthalic anhydrides. The products are useful chemical intermediates for the further preparation of various compounds such as the corresponding dicarboxylic acids and the various derivatives thereof, including for example, the salts, esters, acyl halides, amides, imides and the like. The oxy-diphthalic anhydrides are particularly useful as monomers in the preparation of polyimides, for example by polycondensation with a suitable diamine, such as ethylenediamine or phenylenediamine.
Various methods for the preparation of oxy-diphthalic anhydrides have been described in the chemical literature. One such method, shown to be useful in the preparation of oxy-diphthalic acids and anhydrides, involves the oxidation of tetramethyl diphenyl ethers. See Kolesnikov, G. S. et al Vysokomol. Soyed, A9, 612-18 (1967); Marvel, C. S. et al, J. Am. Chem. Soc. 80. 1197 (1958); and Latrova, Z. N. et al. Volokna Sin. Polim., 15-24 (1970).
Three Japanese patents assigned to Mitsui Toatsu Chemicals, Inc. describe preparations based on reactions of substituted phthalic anhydrides. Japanese Patent Document No. 80/136, 246 (Chem. Abst. 95:42680) teaches the coupling of 4-nitrophthalic anhydride in the presence of sodium nitrite or potassium nitrate to form oxy-diphthalic oxy-diphthalic anhydride. Japanese Patent Document No. 80/122, 738 (Chem. Abst. 94:83799) discloses the reaction of 4-halophthalic acid or anhydride with an alkali metal hydroxide to yield oxy-diphthalic anhydride. In Japanese Patent Document No. 80/27, 343 (Chem. Abstr. 94:191942) the reaction of 4-halo-phthalic anhydride, Na.sub.2 CO.sub.3 and NaNO.sub.2 in dimethyl sulfoxide to form 4,4'-dihydroxydi- phthalylic anhydride is described.
German Patent No. 2,416,594 (1975) discloses the coupling of 3-nitrophthalic anhydride in the presence of metal nitrites, such as sodium nitrite to form oxy-diphthalic anhydride.
Markezich, R. L. and Zamek, O. S. J. Org. Chem. 42, 3431 (1977) describe reaction of 4-nitrophthalimide with potassium fluoride in dimethylsulfoxide to form the corresponding oxy-diphthalimide which may be converted by hydrolysis to form the acid and ring closure to form the dianhydride.